John Gunn — Causes of Change of Climate. 73 



my father considered might be Upper Freshwater only from their 

 eastward position (pointing out that the shells in them were the 

 same as in those beneath the marine bed), they have shown nothing 

 beyond, or contrary to, what he stated ; and it is obvious that it will 

 require further excavations between the two points to determine 

 whether the Freshwater beds a third of a mile to the east are, or 

 are not, beneath the marine bed which this party opened. If such 

 be done, and Mr. Keeping's view that they are beneath it is con- 

 firmed, this, so far from showing my father to have been wrong, will 

 show him to have been right in so cautiously guarding himself 

 against any more positive assertion as to the geological position of 

 these freshwater beds to the east of the ravine, than appears from the 

 extracts which I have given from his paper. 



lY. — On the Causes of Change of Climate from Warm to 

 Cold, and Cold to Warsi, During Long Periods, and also of 

 Coincident Changes of the Fauna and Flora.^ 

 By John Gunn, M.A., F.G.S. 



T is a trite observation that truths which lie at our feet may be 

 overlooked by the wise, and discovered by mere accident, 

 or the chance step of some casual passer-by. 



This appears to be the case with the phenomena of the so-called 

 Glacial epoch, and the causes of the change of temperature on the 

 earth's surface. The depth and the height of science have been 

 searched through heaven and earth, while the grand and simple 

 agency of nature, which has been operating alike through all time, 

 may have been overlooked, or not duly consulted. 



To enter upon the subject at once : it may be asked, if the eleva- 

 tion of mountain ranges be productive of cold, why may not the 

 converse be true, and the wearing down and levelling of those 

 heights be the cause of a warm temperature ? 



This is not a matter of conjecture, but from its very nature 

 it ought to be a subject of observation, and to admit of actual 

 verification. 



In pursuing this inquiry, it is not necessary to enter into the 

 question, how the inequalities of the earth's surfuce may have 

 originated, nor to refer to astronomical agencies, such as the Pre- 

 cession of the Equinoxes, which are perpetually and uniformly at 

 work alike under all conditions of elevation or depression ; but 

 I will claim in support of my proposition, the effect produced by the 

 alterations of the course of the Gulf Stream, through changes in the 

 level of the land, and also by the transport and melting of icebergs 

 and glaciers. 



With these provisos, I will commence my observations with the 

 Carboniferous epoch. There is evidence of a quiescent state during 

 which coal was deposited. Not a single instance, that I am aware, 

 can be adduced of the occurrence of bouldered rocks, certainly not of 



' A Paper read before the Geological Section of the Meeting of the British Asso- 

 ciation at Southport, 1883. ■ 



